Why does my TU5300sc or TU5400sc read higher/lower than my 1720E, FT660, or Ultraturb analyzers?

Document ID

Document ID TE6654

Published Date

Published Date 06/07/2018
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Question
Why does my TU5300sc or TU5400sc read higher/lower than my 1720E, FT660, or Ultraturb analyzers?
Summary
Troubleshooting questions to help determine discrepancies in readings between TU5 Series and older Hach turbidimeters.
Answer
  • Calibration standards
    • Have all instruments involved been calibrated recently? Were calibration standards within expiration at the point of calibration?
  • Lamp replacement (1720E only)
    • Incandescent lamps will dim over time, potentially causing issues with calibration. To ensure accurate readings from the 1720E, its incandescent bulb must be replaced annually.
  • Comparison between process TU5 and TU5200
    • Following the instructions available in the user manual for the TU5200 or TU5300 and TU5400, complete a comparison between lab and process. If lab and process do not match within criteria, follow the steps presented on the TU5200 screen to troubleshoot until matching values occur.
  • Pressure and flow
    • Is sample pressure coming into both instruments within the recommended range?
    • Is sample flow coming into both instruments within the recommended range?
    • Does sample flow coming into and out of each individual instrument match?
    • Does sample flow match between instruments? Having similar flow rates removes a variable when comparing instruments.
  • Proper Maintenance
    • 1720E and FT660
      • If not cleaned per specifications in the manual and if paired with low flow, residue can build up inside the instrument due to premature settling and cause lower than actual readings.
    • Ultraturb
      • When a wiper is not installed, if the instrument is not cleaned per specifications in the manual and if paired with low flow, residue can build up inside the instrument due to premature settling and cause lower than actual readings.
    • TU5 Cleaning Frequency
      • If not cleaned per specifications in the manual (and at a frequency appropriate to the application), residue can build up on the inside of the sample cell, increasing turbidity values.

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